In general, high-precision products such as semiconductor elements or substrates require high precision, and thus, high cleanliness and special production technology have been demanded.
For this reason, the high-precision products are favorably manufactured in a vacuum state in which foreign substances contained in air are completely prevented from contacting the devices.
Thus, a technique of sealing the vacuum work zone of a semiconductor manufacturing apparatus from the atmosphere has crucial influence on the quality of high-precision products.
Accordingly, in a manufacturing process of high-precision products, a gate valve is used to selectively construct instantaneous vacuum environment.
Such a gate valve is roughly classified into two types—a single-direction type and a bidirectional type—and a type suitable for the characteristics of the manufacturing process is selected and installed.
In particular, in the case of the bidirectional type gate valve, a movement space of a high-precision product may be selectively closed, and when only the movement space on one side has been set to be closed and a problem occurs in closing the movement space on the one side, the movement space on the other side may be set to be closed, and thus, it is possible to ensure a continuous operation.
Among such a bidirectional gate valve, a “bidirectional gate valve (Korean Patent Registration No. 10-1258240)” of patent document 1 below, includes: a sealing member 110 which is operated in the up-down and front-rear directions inside a vacuum housing 10 provided with openings 11 and 12 respectively having an open front surface an open rear surface and thereby seals the openings 11 and 12; a man shaft 120 which is provided in a first valve housing 20 perpendicularly connected to a lower portion of the vacuum housing 10 and has an upper portion coupled to a lower portion of the sealing member 110;
a valve driving part 130 which is provided to the first valve housing 20, and is provided with: a main cylinder 131 coupled to a lower portion of the main shaft 120; and a main piston 132 installed inside the main cylinder 131, raised or lowered according to the increase/decrease in compressed air supplied into the main cylinder 131, and connected to the main shaft 120; a first moving unit 140 which is provided to an upper portion of a second valve housing 30 vertically connected to a lower portion of the first valve housing 20, coupled to a lower portion of a valve driving part 130 via a first link 40, and thereby rotates the valve driving part 130; a second moving unit 150 which is provided to an upper portion of the second valve housing 30, coupled to the lower side of the valve driving part 130 via a second link 50, and thereby rotates the valve driving part 130; a first rotation driving part 160 which is provided to a lower part of the second valve housing 30, and is provided with: a first piston shaft 161 coupled to a lower portion of the first moving unit 140 and vertically moved; and a first piston 162 into which a first piston shaft 161 is inserted and which is vertically moved; a second rotation driving part 170 which is provided to the lower portion of the second valve housing 30, and is provided with: a second piston shaft 171 coupled to a lower side portion of the second moving unit 150 and vertically moved; and a second piston 172 into which the second piston shaft 171 is inserted and which is vertically moved; and second valve driving parts 180 and 190 which are provided to the lower portion of the second valve housing 30 and which respectively raise or lower the first piston 162 and the second piston 172 of the first rotation driving part 160 and the second rotation driving part 170 according to an increase/decrease of compressed air. The first moving unit 140 and the second moving unit 150 include first and second guide bearings 142 and 152 which are respectively guided along first and second guide panels 141 and 151, which are respectively installed on front and rear surfaces of the second valve housing 30, and thereby allow a vertical movement for rotating the valve driving part 130 to be easily carried out via the first link 40 and the second link 50. The first rotation driving part 160 and the second rotation driving part 170 includes a rotation prevention bushing 163 (not shown) which prevents first and second piston shafts 161 and 171 which are provided to the lower portion of the second valve housing 30 in addition to the first and second piston shafts 161 and 171 and the first and second pistons 162 and 172 from being rotated according to the density of the compressed air when being vertically moved by the first and second valve driving parts 180 and 190. The rotation prevention bushing 163 (not shown) is configured as a bushing guide bearing 163a (not shown) inserted into and guided by a guide groove 161a (not shown), which are positioned inside the second valve housing 30 and formed in the lengthwise direction of the first and second piston shafts 161 and 172. Thus, there was a merit of preventing a great amount of stress from being concentrated on the guide bearing and thereby making it possible to prevent the guide bearing to be worn or broken.
However, the “bidirectional gate valve” of said patent document 1 is configured from parallel-type link structures which are respectively provided as the first and second links 40 and 50 in the same plane to horizontally move the sealing member 110. Thus, there was a limitation in that a mechanical defect may occur when the sealing member is horizontally moved, for example, the precision of the sealing is deteriorated because the pressures of the first and second rotation driving parts 160 and 170 and the pressure of the first and second valve driving parts 180 and 190, which function as a cylinder, are smaller than the pressure of a serial-type cylinder.
In addition, since the first and second links 40 and 50 are positioned in the same plane, and the width dimensions of the first and second valve housings 20 and 30 are relatively increased, there was a limitation in that spatial restriction is increased because it is impossible to manufacture the bidirectional gate valve in a compact type.